Oops! Fixes for an Under-Catalyzed Finish

      When you spray conversion varnish without the proper dose of catalyst, is there any remedy short of stripping and starting over? July 29, 2011

I had a brain freeze this morning. First time in 15 years using SW water white conversion varnish. I sprayed a set of cabinets with only 1/4 the amount of required catalyst. Thought it was drying slowly (still is). What now? What are the implications, and are there any possible remedies? Is it possible to just let dry, sand, and topcoat with normally catalyzed product? Do I need to strip it all (almost not possible with these doors)?

Forum Responses
(Finishing Forum)
From the original questioner:
I communicated with SW tech line. The only thing they would recommend was stripping. The finish was still soft, so I did it with xylene. Got harder to do later in the day, but I believe I got it off. Still interested in what others have done in similar situations. Tech support said it happens quite often. Oh well...

From contributor M:
The one time I did that it cost me a new cup for my gun. I threw it across the room after spraying a few doors (before I remembered the cat). I also mark my catalyst bottles, after using the wrong one. Stripping was my only answer. I am interested to know if anyone has a fix.

From contributor B:
Stripping is your only solution. The catalyst must be able to force the resins to crosslink and oxidize (makes it dry). I've heard of guys mixing catalyst with thinner and spraying it on the surface, claiming it worked fine, but there's no way the catalyst can work its way through the coating film and be able to do the job anywhere near correctly. Stick with the hard work and remember the lesson learned.

From Paul Snyder, forum technical advisor:
Try an experiment. Mix up a small batch of the under-catalyzed material and spray a test panel. Let it sit for about the same amount of time it took you to realize your mistake. Then mix up a small batch of properly catalyzed finish and spray a coat over the first without any sanding.

Let it dry for a day and sand half of the panel and spray that half with another coat of properly catalyzed finish. Let it cure completely per the time listed on the data sheet and then see how resistant it is to solvents and scratching on both ends of the panel.

From the original questioner:
I am in the process of lightly sanding and reblending the stain to try to get it even (where the xylene took off more in some places). I did shoot some test panels with the under catalyzed finish. I'll spray tomorrow and let you know how it turned out. One thing, the finish on the test panels never really hardened totally. I can make fingerprints in them. Also they're glossy, whereas the finish is dull rubbed.

From contributor S:
Been there, done that. Had to wipe it all off with xylene and start over too. Let's just say I'll do my best to never have it happen again - it was a miserable experience.

From the original questioner:
Resprayed everything. Yes, I did make sure there was the right amount of catalyst. Funny, it's drying like normal.

From contributor I:
I have had two similar experiences - one, no catalyst; the other I used the catalyst for the sealer by mistake. I knew from seeing it spilled on our mixing table and floor that it gets hard without the catalyst; it won't stay wet forever. Sanding wasn't an option. Maybe if I left it sit for a day or two, but I'm not that patient. I mixed up a batch with about 50% extra cat and thinned 15% with naphtha. Sprayed a light wet coat. It took maybe an hour to dry till I could sand. I usually start sanding after 30 minutes, but it came out fine. By the time I put the last coat on it was like it never happened.

I first started using these coatings about 2 1/2 years ago. These two jobs were some of the first I did and both have held up fine - one is a master bath vanity and the other a bar in an executive's office, and both get daily use.

From the original questioner:
Is it the SW water white CV you are using? That's a neat trick. I'll put it away for a trick to pull out of the hat. I'm going to try to never need it.

From contributor I:
Yeah, same SW products. The only others I've tried were Mohawk, and I couldn't ever get close to the quality of the SW finishes no matter what I did. When I first started reading this post I cringed at the idea of stripping - I've tried a few times but could never get back close enough to the original quality (stain wise) and ended up replacing in the end.

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